The present invention relates to composite crimped bundles of filament yarns and a method of producing such bundles of filament yarns. More specifically, the present invention is concerned with composite crimped filament yarns resembling spun yarns in their external appearance and a method of preparing such filament yarns.
Various methods have heretofore been proposed for preparing filament yarns which closely resemble spun yarns by the use of long filaments. One method employs a widely used spindle type false-twisting apparatus to perform false-twisting of two filament yarns simultaneously. This method, however, involves a drawback in that the two filament yarns once coiled together in a position upstream of a spindle become separated again in another position downstream of the spindle due to a large magnitude of tension applied to the yarns in a de-twisting zone. The result is insufficient twining of monofilaments of one yarn round those of the other as shown in FIG. 17 of the accompanying drawings. Another shortcoming inherent in this type of method is that such a tension in the de-twisting zone adds to the liability of breakage of filament yarns and, hence, impairs the efficiency. Another method relies on a friction type internal or external contact false-twisting apparatus using belts or drums as well known in the art. This method is neither fully acceptable because the tension in the de-twisting zone is too high to insure firm entwinement of the monofilaments of the yarns as in the first-mentioned spindle type process.